A US woman who shot and killed her husband and two adult children before taking her own life is thought to have committed the shocking crime as a result of being ostracised from the religion she was raised in.

A federal judge sentenced a former Arkansas judge Wednesday to five years in prison — a stiffer punishment than prosecutors recommended — after he admitted giving young male defendants lighter sentences in return for personal benefits that included sexual favours.

Every time I tell a mate I’m doing a story on cryptocurrency, they invariably ask me the same two questions: should they invest their own hard-earned money, and which cryptocurrency will get them a Lamborghini/yacht/island quickest?

In a 60 Minutes online exclusive, reporter Liz Hayes quizzed Australian Prime Minister Malcolm Turnbull on his relationship with the unpredictable Twitter aficionado and US president Donald Trump ahead of their meeting at the White House Friday.

Carbon tax flyers 'blatant advertising'

The federal opposition has demanded Labor stop wasting taxpayers' money on carbon tax flyers, which are being mailed out with electricity bills.

The flyer explains only $9 out of every $100 of an average bill is due to the carbon tax.

The flyer also suggests average bills will rise $3.30 a week in 2012/13 due to the carbon tax but households will receive $10.10 a week compensation.

"The brochure is a blatant attempt by the government to try to downplay the impact of the carbon tax on people's electricity bills," opposition climate action spokesman Greg Hunt said in a statement on Tuesday.

"The government is spending $70 million on advertising the carbon tax including a television campaign."

Finance Minister Penny Wong on Tuesday announced the government would save $550 million over four years by cutting unnecessary spending in the public service.

She said Labor had already "reduced the wasteful spending on travel and advertising that took place in the past".